This invention pertains to a magazine for carrying bristles through a brush-making apparatus, and, more specifically, to a magazine which retains all of the bristles with the same force.
The variety of brands, designs, and styles of toothbrushes available in the United States today is truly staggering. Brushes are available in sizes and styles appropriate for babies, adults, dentures, sensitive gums, and other specialized needs. As consumers become more concerned about oral hygiene, manufacturers have designed brushes whose bristles are optimized to reach and clean the irregular surfaces of the teeth. These brushes frequently have bristle bundles with a variety of different shapes and sizes.
The bristle bundles may be inserted into the brush via any of several methods. In an in-mold process, the ends of the bristle bundles are projected into a mold cavity and the handle injection molded around the ends of the bristles, encapsulating the ends of the bristles in the brush. In a fusion process, the handles are produced by injection molding, following which the bristles are inserted into holes in the head of the brush. The holes may be formed during the injection molding or created as part of the fusion process. To fuse the bristle bundles into the brush, either the ends of the bristles are heated or the head of the brush is heated, or both. The bristles are inserted into the holes, and heated material flows to encapsulate the bristles in the holes. Exemplary in-mold bristling processes are described in U.S. Pat. No. 5,143,424 and in our co-pending patent application Ser. No. 09/494,946, filed Feb. 2, 2000, now U.S. Pat. No. 6,523,907, the entire contents of both of which are incorporated herein by reference. Exemplary fusion processes are described in our co-pending patent application Ser. No. 09/465,209, filed Dec. 15, 1999, now U.S. Pat. Nos. 6,260,928, and 4,637,660, the entire contents of both of which are also incorporated herein by reference.
In either of these methods, the bristles must be processed either before or after (or both) being united with the handle. The use ends of the bristles must be polished, or end-rounded, to remove any sharp edges. The bristle bundles themselves may be profiled to vary the length of the bristles within each bristle bundle. In addition, the non-use ends of the bristle bundles are typically fused before insertion into the handle.
Until they are inserted into the handle, the bristle bundles are carried along a brush-making apparatus by a magazine. This magazine clamps the bristles to retain them during the cutting, end-rounding and injection molding or fusion steps and releases them temporarily for the profiling step. If, in an in-mold bristling process, the handle is produced using a two part injection process, then the magazine retains the first injected portion via the bristles while it is transported from the first injection mold to the second. Thus, the clamp in the magazine may have to retain the bristles against a relatively large force.
Thus, it is desirable to have a magazine that can retain the bristles with a consistent force across all bristle bundles without damage to the bristles.
In one aspect, the invention is a magazine for a plurality of bristle bundles. The magazine includes a backplate, a mold plate, and a locking plate disposed between the mold plate and the backplate. A plurality of channels extend through the backplate, mold plate, and locking plate. The channels comprise first, second, and third holes in the backplate, locking plate, and mold plate, respectively. A sliding cam action is slidably disposed within the clamping plate. When the sliding cam action is in a first position, the locking plate retains the bristle bundles in the channels; the bristle bundles are released when the sliding cam action is in a second position. The first and second holes in each channel have a cross-section the same shape and size as a cross-section of the bristle bundles which are designated to be contained in those channels. However, at least a portion of the channels have a second hole having a larger cross-sectional area than the cross-section of the bristle bundles designated to be contained therein. The plurality of second holes in the locking plate may be adapted and constructed to exert the same force on the bristle bundles in each of the channels when the sliding cam action is in the first position. The holes may include a leading side and a trailing side. The trailing side of at least a portion of the second holes of the channels are not aligned with the trailing sides of the corresponding first and third holes in each channel when the sliding cam action is in the first position. The extent of the misalignment need not be the same for all the channels and may be adjusted such that a force exerted on each of the bristle bundles when the sliding cam action is in the first position is equal. The force exerted on each of the bristle bundles when the sliding cam action is in the first position may be at least 0.5, 3, 5, 8, 12, or 18 pounds.
In another aspect, the invention is an improved magazine for transporting bristle bundles. The magazine has a backplate, a mold plate, a locking plate disposed between the mold plate and the backplate, channels traversing the magazine comprising first, second, and third holes in each of the backplate, locking plate, and mold plate, respectively, and a sliding cam action slidably disposed within the locking plate. The locking plate retains the bristle bundles in the channels when the sliding cam action is in a first position and releases them when the sliding cam action is in a second position. The improvement to the magazine comprises an adjustment to the cross-sectional area of the second holes in each of the channels such that the locking plate exerts a consistent force on the bristle bundles when the sliding cam action is in the first position.
In another aspect, the invention is a method for designing a retaining apparatus. The method comprises disposing a bristle bundle having a type in a channel in a testing apparatus having a clamp slidably disposed therein, slidably displacing the clamp to retain the bristle bundle until it exerts a pre-determined force on the bristle bundle, determining the displacement of a trailing side of the channel with respect to a fixed point on the testing apparatus when the clamp exerts the pre-determined force, repeating the steps of disposing and displacing for each additional type of bristle bundle which will be held by the retaining apparatus, and disposing channels in a clamping plate of the retaining apparatus such that, when the clamp of the retaining apparatus is displaced by a pre-determined amount, the trailing sides of the channels in which each of the different types of bristle bundles are disposed are displaced by the determined amount with respect to a point on the retaining apparatus corresponding to the fixed point on the testing apparatus. Bristle bundle type may comprise bristle bundle shape or size, bristle material, or any combination thereof. The force exerted on each of the bristle bundles by the clamp may be at least 0.5, 3, 5, 8, 12, or 18 pounds.